Field Crops

Lately I have received questions as to whether corn at various stages of development, especially the blister (R2) and dough (R4) stages, will mature before the 50% average frost date. According to the National Agricultural Statistics Service, as of August 18, 37 percent of Ohio’s corn acreage was in the dough stage (R4) compared to 70 percent for the five year average, and three percent of the corn acreage was in the dent stage (R5) compared to 21 percent for the five-year average. Many areas of the state corn are considerably behind the five-year average because of late planting. Late maturation of the corn crop had led to questions about the likelihood for frost damage and whether more fuel will be needed to dry corn.

Physiological maturity (R6), when kernels have obtained maximum dry weight and black layer has formed, typically occurs about 65 days after silking. At physiological maturity (kernel moisture approximately 30-35%), frosts have little or no effect on the yield potential of the corn crop.

Dr. Bob Nielsen has summarized research findings from Purdue University and Ohio State University that provide insight into both the calendar days and thermal time (growing degree days, GDDs) typically required for grain at various stages of development to achieve physiological maturity (kernel black layer, R6). This research was conducted at two locations in Indiana (west central and southeast) and two locations in Ohio (northwest and southwest) with three hybrids representing 97, 105, and 111-day relative maturities planted in early May, late May, and mid-June. The calendar days and thermal time from silking to black layer for the 111-day hybrid maturity are shown in Table 1 from http://www.agry.purdue.edu/ext/corn/news/timeless/RStagePrediction.html. The calendar days and thermal time from silking to black layer for the 97-day hybrid and 105 maturity are also available from this Purdue webpage.

The study indicated that corn planted in mid-June compared to early May requires 200 to 300 fewer GDDs to achieve physiological maturity. According to Dr. Nielsen, while slightly different responses among the four locations of the trial existed, there did not seem to be a consistent north/south relationship. Therefore, growers can use the results summarized in the following table to “guesstimate” the number of calendar days or heat units necessary for a late-planted field at a given grain fill stage to mature safely prior to that killing fall freeze.

How many GDDs can be expected from now until an average date of a killing

frost for a 111-day hybrid planted in mid-June? To answer this question, estimate the expected GDD accumulation from Aug. 19 until the average frost date (50% probability) for different regions of the state (Table 2). These GDD expectations are based on 30-year historical normals reported by the Ohio Agricultural Statistics Service. The GDD accumulation was calculated using the 86/50 cutoff, base 50 method.

If you want to determine the “youngest stage of corn development” that can safely reach black layer before the average frost date at a given weather station, use the information in Table 2 on remaining GDDs in conjunction with Table 1 which indicates GDDs needed to reach black layer at various stages of grain fill. Compare “GDDs remaining” for the site with the GDDs required to achieve black layer depending on the corn’s developmental stage.

Table 2. Estimated GDDs remaining from Aug. 9 to the first fall frost for Ohio.

Region

Median Frost Date

(50% probability)

Estimated GDDs Remaining

From Aug. 19 to Fall Frost

Northwest

Oct 10 – Oct 20

673 – 723

North Central

Oct 10 – Oct 25

656 – 741

Northeast

Sept 30 – Oct 25

603 – 749

West Central

Oct 10 – Oct 15

716 – 773

Central

Oct 5 – Oct 15

670 – 796

East Central

Sept 30 – Oct 15

645 – 763

Southwest

Oct 10 – Oct 15

752 – 815

South Central

Oct 15 – Oct 20

841 – 893

Southeast

Oct 5 – Oct 15

651 – 774

If your corn is in the milk stage (R3) as of Aug. 19, will it be safe from frost? Table 1 indicates that corn planted in mid – June required about 681 GDDs to reach black layer from R3 and Table 2 indicates that all regions of the state can accumulate that number of GDDs before the 50% frost date.

However, if your corn is in the blister stage (R2) as of Aug. 19, it might be a different story. The kernel development – GDD accumulation relationships in Table 1 indicate that corn planted in mid-June that is at R2 needs about 781 GDDs to reach black layer. Table 2 indicates that three regions of the state, South Central, Central, and Southwest, accumulate that number of GDDs before the 50% frost date. Several other regions, West Central, and Southeast, come close to accumulating this number whereas, the Northeast, Northwest, and North Central regions are least likely to accumulate the GDDs required to achieve physiological maturity.

The research results in Table 1 demonstrate that late-planted corn has the ability to adjust its maturity requirements, and most of this adjustment occurs during the late kernel development stages. In previous growing seasons when GDD accumulation was markedly less than normal, corn planted by mid-June has usually achieved physiological maturity before the first frost occurred.

Today managing your corn crop requires knowledge of the different growth stages of the corn plant. Growth stage identification is critical for scouting and proper timing of fertilizer and pesticide applications. Throughout the growing season I will discuss the various corn growth stages and management issue at each stage.

R3 – Milk

The R3 (Milk) stage occurs about 18 – 22 days after silking. At this stage the outside of the kernel is colored yellow while the inside is white. The kernel contains a “milky” white fluid that will explode when pressure is applied. Kernel moisture content is approximately 80% and starch is beginning to accumulate in the kernel.

It’s been a while since we’ve written about the Lake Erie Bill of Rights (LEBOR)! As a refresher, LEBOR was passed in February in a special election as an amendment to Toledo’s city charter. LEBOR was meant to create new legal rights for Lake Erie, the Lake Erie ecosystem, and to give Toledo citizens the ability to sue to enforce those legal rights against a government or a corporation violating them. For a longer explanation on LEBOR, see our post here. Since then, lawsuits for and against LEBOR have been filed, and the state of Ohio has passed legislation concerning the language in LEBOR. Updates on those actions will be discussed below.

Update on the Drewes Farm lawsuit

The day after LEBOR passed, Drewes Farm Partnership initiated a lawsuit in the U.S. District Court for the Northern District of Ohio, Western Division, against the city of Toledo. Our initial blog posts concerning this lawsuit are available here and here. In May, we discussed updates to the Drewes Farm lawsuit in yet another blog post. Since our last update, the Lake Erie Ecosystem and TSW’s motion to stay pending appeal and the appeal were both denied, meaning the Sixth Circuit agreed with the district court’s decision to leave the ecosystem and TSW out of the lawsuit. As a result, the current parties to the lawsuit are plaintiffs Drewes Farm Partnership and the State of Ohio, as well as the defendant City of Toledo. In early June, both the Drewes Farm Partnership and the state of Ohio filed motions for judgement on the pleadings. The district court has not yet determined whether to grant the motions; the City of Toledo’s response to the motions is due on August 9, 2019. After the response is filed, the plaintiffs will have a chance to reply.

Night time temperatures can affect corn yield potential. High night temperatures (in the 70s or 80s degrees F) can result in wasteful respiration and a lower net amount of dry matter accumulation in plants. Past studies reveal that above-average night temperatures during grainfill can reduce corn yield by reducing kernel number and kernel weight. The rate of respiration of plants increases rapidly as the temperature increases, approximately doubling for each 13 degree F increase. With high night temperatures more of the sugars produced by photosynthesis during the day are lost; less is available to fill developing kernels, thereby lowering potential grain yield. High night time temperatures result in faster heat unit or growing degree day (GDD) accumulation that can lead to earlier corn maturation, whereas cool night temperatures result in slower GDD accumulation that can lengthen grain filling and promote greater dry matter accumulation and grain yields.

Research at the University of Illinois conducted back in the 1960’s indicated that corn grown at night temperatures in the mid-60s (degrees F) out yielded corn grown at temperatures in the mid-80s (degrees F). Average corn yields are generally much higher with irrigation in western states, which have low humidity and limited rainfall. While these areas are characterized by hot sunny days, night temperatures are often cooler than in the Eastern Corn Belt. Low night temperatures during grain fill (which typically occurs in July and August) have been associated with some of our highest corn yields in Ohio. The cool night temperatures may have reduced respiration losses during grain fill and lengthened the rain fill period. Cooler than average night temperatures can also mitigate water stress and slow the development of foliar diseases and insect problems.

Today managing your corn crop requires knowledge of the different growth stages of the corn plant. Growth stage identification is critical for scouting and proper timing of fertilizer and pesticide applications. Throughout the growing season I will discuss the various corn growth stages and management issue at each stage.

R2 – Blister

The R2 (blister) stage occurs about 10 – 12 days after silking. At this stage the kernel is visible and resembles a blister. The kernel is filled with clear fluid, the embryo is barely visible and it is at about 85% moisture.

Kernels are in a rapid period of grain-fill. Rapid and steady grain-fill will continue through R6. If severe stress occurs now or during R3, kernel abortion will occur from the tip of the ear downward. Kernel abortion will continue until the plant has has enough carbohydrates for the remaining kernels.

Silks outside the husk leaves are drying and changing in color from tan to light brown. The silks will naturally detach from their kernels following fertilization.

Source: farmdoc daily(9):151, Department of Agricultural and Consumer Economics, University of Illinois at Urbana-Champaign, August 15, 2019.

The Farm Service Agency (FSA) of the U.S. Department of Agriculture released county acreages for crops and prevent plantings based on acreage reports filed by farmers. Even though prevent plant totaled 19 million acres in the United States, planted corn acres in 2019 are only slightly lower than 2018 values. With notable exceptions, corn acres decreased in counties that had large areas of prevent planting and increased in acres with little prevent planting. Soybean acres fell over the vast majority of counties in the United States.

FSA Acreage Data

FSA released their first set of 2019 county-level acreage data on August 1 (see Crop Acreage Data of FSA). This data indicated that there were 85.9 million acres of corn planted in the United States, down by 1% from the 2018 plantings of 86.4 million acres (see Table 1)

The 2019 planting number (85.9 million acres) is expected to increase as FSA continues to update values monthly until January 2020. From 2011 to 2018, corn acreage in the final January report averaged 1.8% higher than the initial August report. However, in recent years, the increase has been much lower. From 2016 to 2018, the January value was .7% higher than the initial August value. A 1.3% increase – the average from 2011 to 2018 – would increase 2019 planted corn acres to 87.4 million acres. A .7% increase – the average from 2016 to 2018 – would increase planted acres to 86.4 million acres, roughly the same as the planted acreage for 2018. Continue reading →

Stockpiles of poultry litter can be seen in farm fields across Ohio. While common each year in wheat stubble fields, there are also stockpiles showing up in preventative plant fields.

Poultry litter is an excellent source of plant nutrients and readily available in most parts of the state. Poultry litter can be from laying hens, pullets, broilers, finished turkeys, turkey hens, or poults. Most of the poultry litter in the state comes from laying hens and turkey finishers. Typical nutrient ranges in poultry litter can be from 45 to 57 pounds of nitrogen, 45 to 70 pounds of P2O5, and 45 to 55 pounds of K2O per ton. The typical application rate is two tons per acre which fits nicely with the P2O5 needs of a two-year corn/soybean rotation.

Like all manures, the moisture content of the poultry litter greatly influences the amount of nutrients per ton. Handlers of poultry litter have manure analysis sheets indicating the nutrient content.

Poultry manure for permitted operations needs to follow the Natural Resource Conservation Service 590 standards when being stockpiled prior to spreading. These include:

– located on soils that are deep to bedrock (greater than 40 inches to bedrock)

Farmers who want to apply the poultry litter delivered to their fields are required by Ohio law to have a fertilizer license, Certified Livestock Manager certificate, or be a Certified Crop Advisor. Check with your local Soil and Water Conservation District for proper setbacks from steams, ditches and wells when applying poultry litter.

Many corn fields are still silking (and some are just past the mid-vegetative stages)….so, it may seem a little early to discuss estimating grain yields. However, according to the most recent NASS crop report, for the week ending Aug. 8, 2019, 25% of the corn crop has reached the dough stage (compared to 63% for the 5 year average). Corn growers with drought damaged fields and late plantings may want to estimate grain yields prior to harvest in order to help with marketing and harvest plans. Two procedures that are widely used for estimating corn grain yields prior to harvest are the YIELD COMPONENT METHOD (also referred to as the “slide rule” or corn yield calculator) and the EAR WEIGHT METHOD. Each method will often produce yield estimates that are within 20 bu/ac of actual yield. Such estimates can be helpful for general planning purposes.

THE YIELD COMPONENT METHOD was developed by the Agricultural Engineering Department at the University of Illinois. The principle advantage to this method is that it can be used as early as the milk stage of kernel development, a stage many Ohio corn fields have probably achieved. The yield component method involves use of a numerical constant for kernel weight which is figured into an equation in order to calculate grain yield. This numerical constant is sometimes referred to as a “fudge‑factor” since it is based on a predetermined average kernel weight. Since weight per kernel will vary depending on hybrid and environment, the yield component method should be used only to estimate relative grain yields, i.e. “ballpark” grain yields. When below normal rainfall occurs during grain fill (resulting in low kernel weights), the yield component method will OVERESTIMATE yields. In a year with good grain fill conditions (resulting in high kernel weights), the method will underestimate grain yields.

In the past, the YIELD COMPONENT METHOD equation used a “fudge factor” of 90 (as the average value for kernel weight, expressed as 90,000 kernels per 56 lb bushel), but kernel size has increased as hybrids have improved over the years. Dr. Bob Nielsen at Purdue University suggests that a “fudge factor” of 80 to 85 (85,000 kernels per 56 lb bushel) is a more realistic value to use in the yield estimation equation today. https://www.agry.purdue.edu/ext/corn/news/timeless/YldEstMethod.html

According to Dr. Emerson Nafziger at the University of Illinois under current drought stress “…. If there’s a fair amount of green leaf area and kernels have already reached dough stage, using 90 [as the “fudge-factor “] might be reasonable. It typically doesn’t help much to try to estimate depth of kernels at dough stage, when kernel depth is typically rather shallow anyway, especially if there are 16 or more kernel rows on the ear. If green leaf area is mostly gone, however, and kernels look like they may be starting to shrink a little, kernels may end up very light, and using 120 or even 140 [as the “fudge-factor”] might be more accurate”. http://bulletin.ipm.illinois.edu/article.php?id=1695.

Today managing your corn crop requires knowledge of the different growth stages of the corn plant. Growth stage identification is critical for scouting and proper timing of fertilizer and pesticide applications. Throughout the growing season I will discuss the various corn growth stages and management issue at each stage.

R1 – Silking

Plants defined as Rl must have one or more silks extending outside the husk leaves. This occurs about 55 to 66 days after emergence. Silks grow about 1 to 1.5 inches per day. Plants are at maximum or near maximum height and have near maximum vegetative dry matter. Silking (Rl) is the only reproductive stage defined not on the characteristics of individual kernels. Determining the reproductive stage of the crop at and after Rl is based solely on the development of the primary ear.

The silking period is the most sensitive period for the crop; stress at this time can reduce kernel number per ear. Silks on the primary ear must be present while pollen shed occurs for successful pollination and fertilization. Synchronization between pollen shed and silking is important for obtaining high grain yields.

During Rl, both pollination and fertilization occur. Each silk is attached to one potential kernel. A pollen grain can land anywhere on an exposed silk and may germinate leading to fertilization. Silks remain receptive to pollen for a minimum of five days after they emerge. The first silks to emerge from the husk leaves are those attached to potential kernels near the base (butt) of the ear. Silks attached to potential kernels at the ear tip are last to emerge and may not be pollinated if pollen shed has ended. Some potential kernels will simply not develop into harvestable kernels due to a failure in pollination or fertilization; these kernels will be visible on the ear as small, undeveloped white mounds. As the plant approaches R2, kernels expand and have angled sides and a flatter top.

At Rl, the ear is at the beginning of a rapid elongation period and is only 40 to 45% of its final length. Potassium uptake is essentially complete and nitrogen and phosphorus uptake is rapid in the plant. Nutrient content by leaf analysis is highly related to the final grain yield at this time. A response to previously applied fertilizer can be seen.

One of the corn production scenarios agronomists least like is an exceptionally wet spring followed by a hotter and drier than normal July and August. The spring of 2019 was one the wettest on records throughout much of the state and now, as the dry weather that started in July persists, such a scenario seems to be a possibility in many Ohio corn fields. A combination of warm temperatures and inadequate rainfall is beginning to stress corn fields across Ohio. What’s exacerbating this problem are the marginal roots evident in some corn fields. Several factors, including poor planting conditions, surface/sidewall compaction and/or excessively wet soil conditions in June have inhibited good root development in many fields. With the onset of drier, warmer conditions in July, these small, shallow root systems have been unable to extract water deeper in the soil profile. Cooler weather and the possibility of storms later in the week may ease drought stress, which is important because many late planted corn fields (planted throughout June) are near or entering the pollination period, the stage of development most susceptible to drought. Other fields past pollination are vulnerable to kernel abortion, which drought conditions increase.

Corn is at many different stages of development because of the wide range in planting dates. To estimate the impact of dry hot weather on corn yield potential, let us review the effects of moisture deficits on corn growth and development from the late vegetative stages, prior to pollination, to the dent stage of kernel development. Yield losses to moisture stress can be directly related to the number of days that the crop shows stress symptoms during different growth periods. The following summarizes findings of past Iowa work that shows the potential impact of water stress on yield potential. Continue reading →

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